The Rates of Mercuration of the Monoalkyl- and the Polymethylbenzenes. Calculation of Relative Reactivities for the Mercuration Reaction<sup>1,2</sup>

Brown, Herbert C.; McGary, C. W.

doi:10.1021/ja01613a083

Cited by 29 publications

(10 citation statements)

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“…Since starting materials and products showed little absorption in the above range, an intermediate complex had been formed. The situation was thus very similar kinetically to that observed for Diels-Alder reactions9 and indeed is a rather common mechanistic scheme which can be generally represented as in equation (2) where C is a rapidly formed intermediate complex.…”

Section: Resultssupporting

confidence: 73%

Kinetics and mechanism of mercuriation of aromatic compounds by mercury trifluoroacetate in trifluoroacetic acid

Fung¹,

Khorramdel-Vahed²,

Ranson³

et al. 1980

J. Chem. Soc., Perkin Trans. 2

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The mercuriation of a series of aromatic derivatives by mercury(l1) trifluoroacetate in trifluoroacetic acid has been studied using titrirnetric and spectrophotornetric methods. The latter method has revealed the presence of a rapidly formed x-complex intermediate and values of the thermodynamic parameters of its formation have been computed. Only small kinetic isotope effects were found for the complex-forming step in contrast to the large values obtained for the slow step. The effect of added salts was investigated and the mechanism of the reaction discussed in detail in the light of these results. Mercuriation by a readily synthesised mixed acetate, Hg(OCOCF,)-(OCOCH,), is also reported as well as some preliminary studies of triptycene derivatives.

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Section: Resultssupporting

confidence: 73%

Kinetics and mechanism of mercuriation of aromatic compounds by mercury trifluoroacetate in trifluoroacetic acid

Fung¹,

Khorramdel-Vahed²,

Ranson³

et al. 1980

J. Chem. Soc., Perkin Trans. 2

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“…We first restudied the competitive mercuration of toluene and benzene with mercuric trifluoroacetate in trifluoroacetic acid at ambient room temperature (220). [The rates of mercuration of monoalkyl-and polymethylbenzenes with mercuric acetate in acetic acid have been determined (15).] The products were precipitated as aryl mercuric bromides, filtered off, and then convertedby bromination into bromobenzene and the corresponding bromotoluenes, which were analyzed by gas/liquid chromatography.…”

Section: Methodsmentioning

confidence: 99%

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Oláh

Hashimoto

Lin

1977

Proc. Natl. Acad. Sci. U.S.A.

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The mercuration and thallation of benzene and substituted benzenes was studied with mercuric and thallic trifluoroacetate, respectively, in trifluoroacetic acid. With the shortest reaction time (1 sec) at 00, the relative rate of mercuration of toluene compared to that of benzene was 17.5, with the isomer distribution in toluene of: ortho, 17.4%; meta, 5.9%; and para, 76.7%. The isomer distribution in toluene varied with the reaction time, significantly more at 25°than at 00. The competitive thallation of benzene and toluene with thallic trifluoroacetate in trifluoroacetic acid at 150 showed the relative rate, toluene/benzene, to be 33, with the isomer distribution in toluene of: ortho, 9.5%; meta, 5.5%; and para, 85.0%. With increasingly higher reaction temperatures in both mercuration and thallation reactions of aromatics, isomerization (both intramolecular and intermolecular) within the relevant ortho-and para-metallated intermediate ions and/or of the isomers becomes more important. Competitive rates and isomer distributions of mercuration and thallation of benzene and substituted benzenes were also determined. The predominant para substitution in both mercuration and thallation of methylbenzenes reflects, besides some steric factors, the strong stabilizing effect of para methyl groups on the arenium ion intermediates. Under predominantly kinetically controlled conditions, no anomalous increase in the amount of meta substitution was observed.The mercuration of aromatic hydrocarbons with mercuric trifluoroacetate in trifluoroacetic acid at 250 has been studied, predominantly by Brown and coworkers (1-3). The rate ratio of toluene to benzene (kT/kB) was found to be 9.89 and the isomer distribution in toluene was: ortho, 12.2%; meta, 8.6%; and para, 79.2%. From these results, as well as from their preceding studies in acetic acid solution with perchloric acid catalyst giving kT/kB = 3.6-7, and 12-16% meta isomer, it was concluded that the relatively high meta isomer ratio observed was due to the high electrophilic reactivity of the mercurating agent causing the observed low selectivity substitutions. These results were correlated by the so-called Brown selectivity relationship (for a review, see ref. 4).It should be pointed out that, in their original paper on mercuration of toluene and benzene, Brown and Nelson, (5) extending the claimed quantitative selectivity relationship governing isomer distributions in aromatic substitution, commented on the preceding work of Klapproth and Westheimer (6) who found that, in glacial acetic acid with perchloric acid as catalyst, toluene was mercurated by mercuric acetate at 250 to give 6% of the meta isomer. Brown and Nelson claimed to have observed 12% meta isomer under similar conditions and stated "we are, however, unable to account for the differences between the values of the meta isomer." In the former case (6), a precise radiochemical technique was used in establishing orientation, whereas infrared analysis was utilized in the latter. iments at 250 and quenc...

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“…However, C-H bond activation mechanisms are difficult to study due to the complex interactions between the reaction parameters [ 15 , 16 ]. Early mechanistic studies proposed an electrophilic aromatic substitution mechanism [ 17 , 18 , 19 ], for which large primary kinetic isotope effects were observed [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Study of Copper-Catalyzed C-H Hydroxylation/C-S Coupling by ESI-HR MS and DFT Calculations

Cai

Zhou

et al. 2017

Molecules

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The reaction mechanism of Cu-catalyzed C-H hydroxylation/C-S coupling was studied using electrospray ionization high resolution mass spectrometry (ESI-HR MS) and density functional theory calculations (DFT). Notably, a series of CuI and CuIII complexes were observed as key intermediates and identified using ESI-HR MS. Furthermore, a catalyst cycle involving proton abstraction/oxidative addition/reductive elimination was proposed. This study is important and valuable with respect to C-H functionalization.

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The Rates of Mercuration of the Monoalkyl- and the Polymethylbenzenes. Calculation of Relative Reactivities for the Mercuration Reaction^1,2

Cited by 29 publications

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Kinetics and mechanism of mercuriation of aromatic compounds by mercury trifluoroacetate in trifluoroacetic acid

Kinetics and mechanism of mercuriation of aromatic compounds by mercury trifluoroacetate in trifluoroacetic acid

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Mechanistic Study of Copper-Catalyzed C-H Hydroxylation/C-S Coupling by ESI-HR MS and DFT Calculations

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The Rates of Mercuration of the Monoalkyl- and the Polymethylbenzenes. Calculation of Relative Reactivities for the Mercuration Reaction1,2

Cited by 29 publications

References 0 publications

Kinetics and mechanism of mercuriation of aromatic compounds by mercury trifluoroacetate in trifluoroacetic acid

Kinetics and mechanism of mercuriation of aromatic compounds by mercury trifluoroacetate in trifluoroacetic acid

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Mechanistic Study of Copper-Catalyzed C-H Hydroxylation/C-S Coupling by ESI-HR MS and DFT Calculations

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The Rates of Mercuration of the Monoalkyl- and the Polymethylbenzenes. Calculation of Relative Reactivities for the Mercuration Reaction^1,2